X-rays can be useful for many applications, including without limitation imaging, electrostatic dissipation, x-ray fluorescence, and x-ray diffraction, but x-rays can also be harmful. X-ray sources can emit x-rays in all directions, including undesirable, and potentially-harmful, directions. It can be important, therefore to block x-rays emitted in undesirable directions.
Thick, high-density materials may be needed for blocking x-rays. The cost of such materials can be undesirable. The weight and size of such materials can be undesirable, especially in portable x-ray tubes.
X-ray tubes can include an electron-emitter that emits electrons towards a target material. The electron-emitter can emit these electrons due to a large voltage between the electron-emitter and the target. An electrically-insulative enclosure, such as glass or ceramic, can separate the electron-emitter from the target. When these electrons hit the target, x-rays and additional electrons are emitted. Some of these additional electrons can fly back into an evacuated region between the target and the electron-emitter, and can hit and be adsorbed onto a surface of the electrically-insulative enclosure. An electrical arc can cause failure of the x-ray tube if enough electrons are thus adsorbed.